Commonly assigned U.S. Pat. Nos., 4.900,234; 4,907,414 and 5,077,981 each disclose a low side hermetic compressor in which a portion of the discharge of the compressor is bled into the oil sump. The high pressure gas being bled into the oil sump represents a loss but, because the interior of the compressor shell and the oil sump are at suction pressure, the foam generated by the high pressure gas expanding to suction pressure in the oil provides sound attenuation.
Discharge gas pulsation in the shell cavity beneath the motor in a high side vertical, hermetic rotary compressor has been found to be one of the major noise sources. In current compressor designs, the compressed gas discharges from the pump structure into the muffler cavity and then passes into the lower shell cavity. The discharge gas passes from the lower shell cavity to the discharge at the top of the compressor shell by passing through the gap between the rotor and stator and/or passing through passages between the stator and the compressor shell.
According to the teachings of the present invention the discharge gas in a high side rotary compressor passes from the pump structure into the muffler cavity and then passes via tubes into the oil sump located beneath the pump structure. Discharging the hot high pressure gas into the oil sump heats the oil and thereby reduces its viscosity. Additionally, the discharging of the high pressure gas into the oil sump, which is also at discharge pressure, generates foam roughly in the volume of the gas discharged from the pump structure. The foam will pass from the oil sump, through the pump structure to the upper part of the lower shell cavity, i.e. the part below the motor. Any foam entering the gap between the rotor and stator will tend to be collapsed and the oil will tend to be centrifugally separated such that it collects on the stator and drains due to gravity.
It is an object of this invention to reduce rotary compressor noise due to discharge gas pulsation.
It is another object of this invention to provide additional attenuation without reducing efficiency.
It is a further object of this invention to improve oil lubrication capability by increasing oil temperature in the sump. These objects, and others as will become apparent hereinafter, are accomplished by the present invention.
Basically, the entire discharge flow in a high side, vertical, hermetic rotary compressor is directed into the oil sump which generates foam for sound attenuation and heats the oil to reduce its viscosity and to drive off refrigerant dissolved in the oil.